Ribbon grid for electron tubes

ABSTRACT

A grid for an electron tube comprises an axially extending helically wound continuous flat metallic strip or ribbon. The smallest dimension of the grid is along the length of the tube and is positioned in the lateral path of electrons between an inner central cathode and an outer concentric anode to minimize electron interception and excessive heating of the grid. The thin edges of the ribbon are secured in peripheral slots along a plurality of longitudinal support rods disposed around a circular area. The larger flat surfaces of the ribbon, extending in a transverse direction from the support rods, provide improved structural rigidity and heat dissipation.

United States Patent 51 3,683,229

Tritchler 1 Aug. 8, 1972 [54] RIBBON GRID FOR ELECTRON TUBES Primary ExaminerDavid Schoznberg Inventor: Joseph J. Tritchler, Bethlehem, Pa.

Assignee: International Telephone and Telegraph Corporation, Nutley, NJ.

Filed: Oct. 26, 1970 Appl. No.: 84,033

US. Cl ..3l3/350, 313/349 Int. Cl ..H0lj 19/38 Field of Search ..3l3/350, 349; 29/2518 References Cited UNITED STATES PATENTS 6/1930 Schwerin ..3l3/350 X 11/1936 Rothe ..3l3/350X 1/1926 Lebbink ..313/35O 8/1953 Werner ..3l3/35O 6/1954 Eisan .313/350 Assistant Examiner-Paul A. Sacher Attorney-C. Cornell Remsen, Jr., Walter J. Baum,

Paul W. l-lemminger, Charles L. Johnson, Jr., Philip M. Bolton, Isidore Togut, Edward Goldberg and Menotti J. Lombardi, Jr.

[57] ABSTRACT A grid for an electron tube comprises an axially extending helically wound continuous flat metallic strip or ribbon. The smallest dimension of the grid is along the length of the tube and is positioned in the lateral path of electrons between an inner central cathode and an outer concentric anode to minimize electron interception and excessive heating of the grid. The thin edges of the ribbon are secured in peripheral slots along a plurality of longitudinal support rods disposed around a circular area. The larger flat surfaces of the ribbon, extending in a transverse direction from the support rods, provide improved structural rigidity and heat dissipation.

5 Claims, 4 Drawing Figures PATENTEnws a ma 3.683.229

INVENTOR JOSEPH J. TRITCHLER BY g ATTORNEY 1 RIBBON GRID FOR ELECTRON TUBES BACKGROUND OF THE INVENTION heat dissipation and structural rigidity for high power tubes.

2. Description of the Prior Art Electron tubes have generally employed helical grids which are made of round wire wound along vertical support rods and bonded thereto and/or supported in notches along the rods. Examples of such prior art structures are found in U.S. Pat. No. 2,829,298 issued Apr. 1, 1958 and U.S. Pat. No. 3,158,777 issued Nov. 24, 1964. Some high power tubes have utilized a plurality of separate parallel vertical flat ribbon members positioned around a central cathode and presenting the thin edge dimension in the lateral electron path between the cathode and an outer concentric anode. The vertical members are joined at the ends and other locations along the length by a plurality of individual peripheral rings which provide structural support. The round grid wires present the maximum surface of the wire diameter in the electron path which results in excessive interception grid current while providing a minimum surface for heat radiation and dissipation. The vertical ribbon members are restricted in the size that can be used, have poor electrical control due to mechanical limitations and are not sufficiently stable or rigid to inhibit longitudinal bending or torsional movement.

SUMMARY OF THE INVENTION It is therefore the primary object of the present invention to provide an improved grid structure for an electron tube which exposes a minimum surface to electron interception and a maximum surface for heat dissipation while providing firm structural support and stability. This is accomplished by a novel ribbon grid configuration which is helically wound around axially extending support rods or posts. The small dimension edges of the grid are disposed in the electron path between an inner cathode and outer concentric anode and secured in longitudinally spaced slots around the periphery of the rods. The continuous flat surfaces of the grid extend in a transverse direction from the rods to provide heat dissipation and structural rigidity. The details of the invention will be more fully understood and other objects and advantages will become apparent in the following description and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows a partial side view of a grid and support rod arrangement in accordance with the invention,

FIG. 2 shows a plan view of the novel grid and support' rod configuration disposed between a central cathode and outer concentric anode;

FIG. 3 is an angled side view of an enlarged portion of the grid and notched support rod, and

FIG. 4 is a plan view of an enlarged portion of the grid and support rod.

2 DESCRIPTION or THE PREFERRED EMBODIMENT As shown in the various figures, a flat ribbon grid 10 is helically wound in a preferably continuous metallic strip around a plurality of longitudinal metal support rods or posts 12 positioned about a central circular area. The thin edges 14 of the ribbon are disposed along the longitudinal tube axis so that electrons, emitted in a lateral path between a central longitudinal cathode 15 and an outer concentric anode 17, as shown in FIG. 2, will be presented with a minimum surface dimension exposed to interception thereby. This reduces grid current and heating of the grid while the larger flat face 16, extending laterally from the rods, provides a maximum surface for increased heat dissipation by radiation and structural rigidity against bending and twisting. The rods, which may be round or of another suitable shape, cause relatively little interference with the electron path or heat dissipation while providing structural support.

The edges 14 of the ribbon are secured in peripheral slots 18 spaced along the length of each support rod 12 so that the helical grid is progressively wound around the rods. The thin edges on one side of the grid are preferably swaged within the slots to form a tight fitting mechanical bond therewith. While the slots may also be disposed on the inner side of. the rods, the arrangement of slots on the outer side provides better mechanical support and simplifies assembly of parts. The ribbon may have laterally curved portions 20 extending around the rods through the slots. This is necessary where critical design considerations require maintenance of a specified inner diameter for the grid so that the rods cannot protrude into the grid-cathode spacing. If this dimension is not critical, the ribbon diameter can remain constant with the rod thickness partially extending into the central area. The extreme opposite ends 22 of the ribbon may be secured in corresponding slots at ends of the adjacent rods.

The ribbon and rods are preferably of a high refractory material such as molybdenum. Typical dimensions of the ribbon may be in the order of 0.008 inches in thickness and 0.025 inches in width. The dimensions of the grid rods for example, may be 0.065 inches in diameter and 6 inches in length. The diameter of the helical grid winding around the rods may be about 2.5 inches and the total number of winding turns may be 60. The slot openings may be in the order of 0.009 inches wide and 0.027 inches deep. While only a single embodiment has been illustrated and described, it is to be understood that other variations may be made in the particular design and configuration without departing from the scope of the invention as set forth in the accompanying claims.

What is claimed is:

l. A grid for an electron tube comprising:

a plurality of longitudinal support rods disposed about a central area, each rod having a plurality of peripheral slots spaced along the length thereof, and

a continuous flat metallic ribbon strip wound progressively around and along said rods, the thin longitudinal edges of one side of said strip engaging and having a tight secure fit within corresponding slots in said rods and the larger surfaces of said strip extending laterally with respect to said rods, said slots having a relatively small longitudinal dimension and a larger lateral dimension accommodating said flat strip.

2. The device of claim 1, wherein said rods are positioned around a circular area and said ribbon grid includes a plurality of helical winding turns around said rods.

3. The device of claim 2, wherein the extreme opposite ends of said strip are secured within slots at the ends of adjacent rods.

4. The device of claim 2, wherein said flat ribbon in- 

1. A grid for an electron tube comprising: a plurality of longitudinal support rods disposed about a central area, each rod having a plurality of peripheral slots spaced along the length thereof, and a continuous flat metallic ribbon strip wound progressively around and along said rods, the thin longitudinal edges of one side of said strip engaging and having a tight secure fit within corresponding slots in said rods and the larger surfaces of said strip extending laterally with respect to said rods, said slots having a relatively small longitudinal dimension and a larger lateral dimension accommodating said flat strip.
 2. The device of claim 1, wherein said rods are positioned around a circular area and said ribbon grid includes a plurality of heliCal winding turns around said rods.
 3. The device of claim 2, wherein the extreme opposite ends of said strip are secured within slots at the ends of adjacent rods.
 4. The device of claim 2, wherein said flat ribbon includes a plurality of laterally curved portions extending around each rod through said slots so that the inner diameter of said ribbon and rods are maintained constant.
 5. The device of claim 1 including a centrally disposed longitudinal electron emissive cathode and an outer concentric anode, said grid being disposed between said anode and cathode, said larger surface of said strip extending substantially parallel to the lateral path of electrons between said cathode and anode with the thin edge being in said path and having a minumum dimension for electron interception. 